1. Introduction
Computer operators and keypunch operators are constantly sitting in front of terminals for extended periods of time. Without taking frequent breaks, operators usually complain of aches and pains in their arms and upper body. Injuries such as carpal tunnel syndrome and pain in the shoulder, neck, arms and upper body can be traced to constant use of standard computer keyboards. It is an object of this invention to provide a means of supporting the keyboard which alleviates the physical discomfort commonly found with repetitive use of such keyboards.
2. Discussion of prior art
Soft tissue disorders, which include both repetitive motion and back injuries, currently account for 39 percent of all United States workers' compensation claims. The annual accounting of occupational illnesses and injuries, as reviewed in the Nov. 16, 1989 issue of the New York Times (A24), shows that reports of repetitive motion disorders have risen from 18 percent in 1981 to 48 percent in 1988. People whose jobs entail frequent computer use, including writers, computer programmers, data entry operators and administrative personnel are considered at risk for contracting these disorders. Back and neck pain are common complaints associated with typing motions for occasional keyboard users. This type pain can also be associated with the uncomfortable position in which the hands are held even over short periods of time.
The most common repetitive motion disorder is carpal tunnel syndrome. It is a nerve condition of the wrist and fingers, often brought about when computer operators type for hours a day using repetitive wrist and finger motions without proper support. The result is damage to the median nerve, which passes from the arm through the wrist into the hand. The nerve supplies the thumb, index finger, middle finger and part of the ring finger with sensation and muscle control. Repeated wrist movements, such as word processing or data entry without proper support, can cause swelling and compress the median nerve. Symptoms include tingling or numb finger, pain in the thumb, index or middle finger, and aching or weakness in one or both arms. Severe CTS cases are often correctable only by surgery. Once limited mostly to meat packers, poultry workers and pianists, it has become a common complaint among workers who use computers or computerized equipment.
Despite improvements in ergonomic design built into today's personal computer keyboards, users still face risk of musculoskeletal injuries directly associated with keyboard use. These injuries are usually referred to as repetitive strain injuries and include tendonitis, arthritis, carpal tunnel syndrome and muscle spasms. These conditions are the result of a combination of overuse and misalignment of the shoulders, elbows and wrist. Shoulder and neck injuries among keyboard users is usually attributed to the table or chair being positioned too high or too low so that the shoulders are held in a crunch position while working or arms have to be stretched to reach the keyboard, resulting in cumulative trauma to the shoulders.
U.S. Pat. No. 4,762,436 discloses a redesigned keyboard with hand positioning structures to eliminate awkward movements and contortions in the hand position while operating a standard keyboard. The hand positioning structures function by the neuro-sensory process of two point discrimination. With minimal practice, use of the hand positioning structures quickly functions at a subconscious reflex level. The hand positioning structures also provide bio-mechanical balance and symmetry for the fingers and hands; improves keyboard operation; reduces operator neuro-muscular stress and fatigue; and facilitates learning how to operate a keyboard.
U.S. Pat. No. 4,669,903 discloses a redesigned keyboard to reduce stress on nerves and tendons in the wrist and hands. The redesigned keyboard evenly divides the keys to be within easy reach of both hands. Instead of the unbroken array of keys in the standard keyboard, the center of the keyboard has a V-shaped division that moves the keys slightly to the left and right. The division places the hands in a more natural position that reduces strain on hand tendons.